Zika virus

February 4, 2016

The World Health Organization (WHO) has declared the Zika virus a public health emergency of international concern. They define this as “an extraordinary event which is to constitute a public health risk to other states through the international spread of disease and to potentially require a coordinated international response.” The WHO estimates that up to 4 million people worldwide could be affected this year. The virus has possibly been linked to thousands of suspected cases of birth defects in Brazil. Zika is primarily spread by bites from infected Aedes aegypti mosquitoes, after which the virus enters the bitten individual’s blood stream. The Aedes albopictus mosquito is also implicated in onward transmission.

As Zika is a flavivirus, which is a relatively large (40nm) lipid-enveloped virus, there is a high probability that it will be successfully inactivated and removed by current viral inactivation (heat, solvent detergent) and removal (nanofiltration) techniques used in the manufacture of plasma-derived medicinal products, including plasma-derived FVIII and FIX concentrates.

Transmission via blood or labile (and not virally inactivated) blood components is more of a potential issue. Transmission is possible through blood donated by viraemic, asymptomatic residents or travellers returning from affected areas. Therefore, blood authorities may consider a temporary deferral from blood donation of persons with a travel history to affected areas (a 28 day deferral, as used for dengue fever).

A blood safety strategy, in affected areas, includes the deferral of donors with a diagnosis of the Zika infection for a period of time from cessation of disease symptoms, pathogen inactivation of platelets and fresh frozen plasma, and enhanced post-donation reporting from donors who develop symptoms compatible with the Zika fever.

The virus was first discovered in the Zika forest in Uganda in 1947. It is common in Africa and Asia. In May 2015, an outbreak occurred in Brazil, and it has now spread to 21 countries in South America, Central America, Mexico, and the Caribbean. Some 60-80% of those infected have no symptoms, and the majority of those who are symptomatic have mild symptoms, including fever with muscle ache, rash, and red eyes. However, there is major concern in relation to a possible impact on pregnant women. In the past year, Brazil has seen a significant increase in the incidence of microcephaly (unusually small brains and heads) in new-born babies. This is suspected to be due to the infection of the pregnant mother with the Zika virus.

There has also been an increase in the number of cases of Guillain-Barre syndrome probably related to an immune response to the virus. There have been some anecdotal reports of transmission by blood transfusion and via sexual contact. On February 2nd, there was a report of sexual transmission of Zika virus in Texas in the USA. Cases of the Zika virus have now been reported in many countries in people who have travelled from affected countries such as Brazil.

The World Federation of Hemophilia (WFH) is monitoring this situation and will update this statement when more information is available, including more details on inactivation of the Zika virus in clotting factor concentrates (CFCs) or any potential risk of transmission from CFCs.